Can't select all of my paid domains for different market

[Protero]

My primairy domain is a .de one for my German shop. I have successfully set up an Italian version with a different domain. Now I'm trying to set up an English version but the domain I want to use for it isn't available in the selection.

It should give me the option "kefirwhey.com" or "proteroco.com" to use the Italian shop and make it an international one.

Thank you in advance for the assistance!